colcothar

Definition of colcothar

plural

-s

1: a reddish brown iron oxide left as a residue when ferrous sulfate is highly heated and used formerly in polishing glass and as a pigment

2: a moderate reddish brown that is yellower and deeper than roan, yellower, stronger, and slightly darker than mahogany, and yellower, less strong, and slightly darker than oxblood —called also angel red, Coromandel, English red, Mars red, Prussian red, Tuscany